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We present an improved design of a nonlinear amplifier loop mirror (NALM) mode-locked Er-fiber laser system with fiber amplifier and compressor contained in all polarization maintaining fiber architecture. Cooperated with a phase shifter in the NALM, the onset behaviors are investigated by optimizing the laser gain and net-cavity dispersion. As a result, the pulsation threshold is remarkably decreased and as short as 10-ms build-up time is achieved. In addition, with a single-stage bidirectional pumped Er-doped fiber amplifier, the self-started seed pulses of 2.6-mW average power, centered at 1576 nm, are nonlinearly compressed to 42-fs duration with single pulse energy of 2.2 nJ. Moreover, by appropriately optimizing the length of cavity gain and fiber in compressor, 28-fs duration with 3-nJ pulse energy is also achieved from a “morning call” pulse with 1567-nm central wavelength. [ABSTRACT FROM PUBLISHER]

We demonstrate a coherent polarization beam combination of two-channel picosecond pulses based on a microcontroller-based phase-locking method. This simple and low-cost technique enables easy programming and automatic relocking of the relative phases between two fiber amplifiers. The total average power of the combined laser is 30.4 W, corresponding to a combining efficiency of 91%. The microcontroller-based phase-locking method provides a competitive solution for robust and programmable control of phases in the active coherent polarization beam combining system. [ABSTRACT FROM PUBLISHER]

In this letter, we present what we believe to be a new design for simultaneously coherent and spectral beam combinations by active phasing and bandwidth-controlled dichromatic mirror. A principle of concept experiment is demonstrated by employing eight 20-W power-level polarization-maintained all fiber amplifiers, which generate a 142.1-W near diffraction limited ( M^2x\sim 1.1 and M^2y\sim 1.1 ) output power with the whole combining efficiency of $>90$ %. The new designed beam combining system is competent for both narrow-band and broadband gain elements with full linewidth of $<4$ nm. Along with the near-diffraction-limited power scaling progress on monolithic polarization-maintained amplifier, we believe that the approach demonstrated has great potential for remarkable power boosting in both continuous- and pulsed-wave operations. [ABSTRACT FROM PUBLISHER]

In this letter, we experimentally investigate the near-diffraction-limited power scaling ability of a high-power narrow-band and polarization-maintained all fiber amplifier chain fed by selecting a small portion of a broadband superfluorescent source. By amplifying the filtered laser based on master oscillator power amplifier configuration, a record power of 800 W is achieved in this type of monolithic amplifier with a slope efficiency as high as 87.7% in the final amplifier and M^2 factor of $\sim 1.3$ . The polarization extinction ratio (PER) and 3-dB bandwidth (FWHM) are measured to be >12 dB and 0.2 ± 0.02 nm, respectively. Further power scaling the amplifier chain, we show that the mode instability effect is occurred, which causes sharply deteriorations of the beam quality and PER. Besides, we show that the influence of self-phase modulation effect and four-wave-mixing effect should also be carefully considered to ensure high portion of narrow-band energy when further enhances this kind of narrow-band architecture. [ABSTRACT FROM PUBLISHER]

We report on supercontinuum generation using a mode-locked VECSEL emitting 400-fs pulses at a 3-GHz repetition rate, amplified with a cascaded ytterbium-doped fiber amplifier system up to 40 W of average power. The pulses are then recompressed to their original duration via a high throughput transmission grating compressor, and used to generate supercontinuum in two samples of photonic crystal fiber (PCF): an all-normal dispersion PCF, and a PCF with a zero dispersion wavelength of 1040 nm, creating 20 dB spectral bandwidths of 200 nm and 280 nm, respectively. [ABSTRACT FROM PUBLISHER]

We demonstrate active coherent polarization locking of two high power polarization-maintained fiber amplifiers using single frequency dithering technique. When the active phasing system is in the closed loop, a 481-W single frequency and polarization-maintained laser beam with near-diffraction-limited beam quality is generated in the circumstance of imbalanced power ratio of the two amplifiers. The beam quality (M^2 factor) of the coherently polarization locked beam is measured to be <1.2 and the polarization extinction ratio of the phasing beam can be as high as 10 dB (91%). [ABSTRACT FROM PUBLISHER]

We demonstrate a coherent polarization beam combining (CPBC) of four all polarization-maintained high-power fiber amplifiers with a total output power of 60 W, using the single-frequency dithering technique. When the control system is in the closed loop, the intensity profile is steady and the phase noise can be suppressed effectively. The experimental results show that the combining efficiency of the whole system is as high as 90% in the circumstance of imbalance power ratios of the four beams. The technique used in this letter can be straightforwardly scaled to CPBC of a large array of high-power fiber amplifiers. [ABSTRACT FROM PUBLISHER]

We investigate the use of dispersion-compensating Raman amplifiers (DCRAs) designed for terminal-only dispersion compensation of a typical 6 × 80 km 10-Gb/s wavelength-division-multiplexing metro link over standard single-mode fiber. The one-stage booster and two-stage preamplifier DCRAs were comprised of high figure-of-merit (400 ps/nm/dB) dispersion-compensating fiber. After transmission, all channels had less than 2.2-dB optical signal-to-noise ratio (OSNR) penalty (at 10-9 bit-error ratio) and more than 7-dB OSNR margin. Further measurements showed that the penalty could be attributed to the large accumulated dispersion during transmission due to the terminal-only compensation, and not to nonlinearities or multiple path interference in the DCRAs. [ABSTRACT FROM PUBLISHER]